1. Field of the Invention
This invention relates to regulating system for a vehicle passenger compartment and, more particularly, to an overheat regulating system which utilizes the latent heat of a phase-change substance circulating between the inside and the outside of the vehicle passenger compartment automatically and can be used to cool overheated passenger compartments of vehicles parked outdoor under direct sunshine in warm weathers without consuming any man-made power.
2. Description of Prior Arts
Entering a sweltering car parked outdoor under sunshine in summer has been an unpleasant and sometimes intolerable experience. The problem is most severe in the presence of direct sunshine due to the greenhouse effect. Experiments have shown that under direct sunshine and with a moderate ambient temperature such as 30.degree. C. (86.degree. F.), the temperature inside a conventional passenger car can easily reach as high as 60.degree. C. (140.degree. F.). There exist some air-conditioning systems in the prior arts which can cool the vehicle after the engine is started. However, none of them can solve the overheat problem effectively since they all need the power from the running engine, which is not available when the car is parked and the driver has left the car.
Conventional automotive air conditioning systems, such as the one described in "Automotive Mechanics" (William H. Crouse, McGraw-Hill 10th Ed., 1996), can effectively cool passenger chambers when engines are running. However, they do not function when automobiles are parked in a parking lot and the engines have stopped running since their compressors need to be powered by the running engines.
There exist some automobile air conditioning units in the prior arts which are different than the conventional air-conditioning systems, but none of them can function when the engines are not running. For example, U.S. Pat. No. 5,477,688 disclosed an automotive air conditioning apparatus utilizing the cooling source obtained from the isothermal expansion of gas in engine. In U.S. Pat. No. 4,051,692, an air-liquid heat-exchanger is used to absorb heat from automobile passenger chamber and release heat to the circulated liquid which is cooled by being sprayed through the air flow at the front of the automobile. The liquid is circulated by using a pump powered by the running engine of the automobile. In U.S. Pat. No. 4,761,967, a thermal storage tank is used to store the cooling energy generated from a conventional cooling circuit and the passenger room can be continuously cooled during the stoppage of the compressor. The cooling energy is transferred from the thermal storage tank to the passenger compartment by a pump which is powered by the running engine.
Another approach existing in the prior arts is to apply a sunlight-proof coating to the glass of car windows. This technique can not solve the problem satisfactorily since the front windshield and the driver-side window glass cannot be coated with the sunlight-proof material to avoid blocking the driver's sight. In addition, the coating can block only 10%-40% of the solar radiation.